Electric pick-up device



Dec. 23, 1930. E. TOMAN 1,786,042

ELECTRIC PI CK'UP DEVICE Filed Sept. 23, 1929 VEU 7U JJMJ/d 75 a Patented Dec. 23, 1930 UNITED STATES PATENT OFFICE EDWARD TOMAN, OF CHICAGO, ILLINOIS, ASSIGNOB 'IO E. TOMAN & 00., OF CHICAGO,

ILLINOIS, A CORPORATION OF ILLINOIS ELECTRIC PICK-UP DEVICE Application filed September 23, 1929. Serial No. 394,429.

This invention relates to an electrical device, and more particularly to an improved electric pick-up device for use in a phonograph or the like, although the device has many other applications, as will be apparent to one skilled in the art.

In the past,- it has been the usual practice to construct electrical pick-up devices with a single permanent magnet provided with pole pieces between which an armature is pivoted. These devices are relatively shortlived, since the magnet itself gradually becomes weaker. Also, in many of the prior art devices, the pivot pin of the vibrating armature has been placed between the pole pieces in such a manner that the effective area of the pole pieces is decreased, with the result that only a portion of the available lines of force are cut by the vibrating armature. Various means have been employed in these devices for centering the armature between the pole pieces and limiting its vibration, but these have been obj ectionable in that the centering is problematical.

It is an object of this invention to provide an electrical pickup device which will maintain a higher efiiciency over a long period of time and one in which the permanent magnet will maintain its magnetic characteristics. 7

It is also an object of this invention to provide a device in which the available lines of force will-not be decreased by the structure of the device.

It is a further object of this invention to provide an improved means for centering the vibrating armature between the pole faces of the magnet and varying the vibration thereof.

Other and further importantobjects of this invention will be apparent from the disclosures in the accompanying drawings and the following specification.

The invention (in a preferred form) is illustrated on the drawings and hereinafter more fully decribed.

On the drawings:

Figure 1"is an elevational view of a device emb dying this invention, which shows Figure 4 is a face view of one of the rubber discs used for centering the armature between the pole faces.

Figure 5 is a top plan view of the permanent horseshoe magnet, showing the rubber discs mounted in grooves in the poles of the magnets and in engagement with the armature.

As shown on the drawings:

In the illustrated embodiment of this invention, the device is shown in Figure 1 enclosed in a stamped metal cover 1 which is secured to the device by screws 2 which pass through the cover and are threaded into a base member 8 (Figure 2), constructed of a non-magnetic material. A peripheral flange 4 projects rearwardly at right angles to the main body of the base member for strengthening the base and providing a wide edge over which the stamped cover is slipped. This flange also provides a surface into which the cover screws extend.

Projecting from the rear side of the base member and at right angles thereto is a circular boss 5having a relatively thin wall 6 integral with the base member and defining a socket for receiving the end of a carriage arm which is not shown. A plug pin receptacle is formed by a stud 7 of insulating material, which is seated in the base'member and prejects forwardly and at right angles there to, said stud containing slotted sleeves 8,

each having one end in communication with the inner end of the above mentioned socket. Plug pins, not shown on the drawings, are arranged in the end of the carriage arm so that, when the carriage arm is inserted in the socket, these pins will make an electrical connection with the sleeves.

A pair of permanent horseshoe magnets 9 are secured to the base member with the pole faces confronting and spaced apart, the north pole of one magnet being adjacent the south pole of the other magnet. Each magnet is supported away from the base member by upraised bosses 10, integral with the body of the base member, and held in position by aplate 11 clamped across the two arms of the magnet by a holding-down screw 12 extending into the base member.

Extending from the pole face to the top face of the upper magnet arm is a beveled edge 13 at an angle of substantially 45, and

a similar beveled edge 14 between the pole face and the forward face of the magnet arm. On the lower arm of the magnet, a beveled edge 15 extends at an angle of substantially 45 from the pole face to the bottom face of the magnet arm, and a similar bevel 16 ex tends from the pole face to the forward face of the magnet arm. By bevelling the magnet poles in this manner, a pole face having a smaller area than that of a cross-section through the magnet arm is provided, thereby increasing the flux density in the pole faces.

A. coil 17 formed by winding an electrical conductor upon a spool having rectangular end pieces 18, of insulating material, is mounted substantially in the center of the base member between the poles of the magnet in such a manner that the side edges of the end pieces will engage in grooves 19 formed in a forwardly projecting stud on the base. A depression 20 is formed in the base member, for receiving edgewisc the coil, in order that the central axis of the coil may be brought more closely to the base member. The coil ends are electrically connected by conductors E21 and 22, respectively, to each of the sleeves 8.

Projecting forwardly from the lower edge of the base member is an apertured bracket 23 for pivotally supporting a stylus bar 2% of non-magneic material, such as brass, which extends through the aperture in a substantially vertical direction. Pivot pins 25 extend through the forward and rear walls of the aperture and engage the stylus bar in a manner that will permit the stylus bar to be vibrated in a plane parallel to that of the base member. The pivot pins are locked in position by lock nuts 26. The lower end of the stylus bar is provided with a socket 2.7 inwardly extending from the end face of said bar, for receiving a. usual stylus or needle, not shown on the drawings.

A. set-screw 28 extends through the for ward side of the stylus bar into the socketfor tightening against the stylus or needle to securely hold it within the socket, sov t the stylus bar will. move responsively to toe movement of the stylus. as follows. the

1.; groove in a phonograph record.

Connected to the upper end of the pivotally mounted stylus bar is. a thin armature, 2,9 which extends between the confronting pole faces of the permanent horseshoe magnets and through a longitudinal aperture 30' of the coil. It is, therefore, evident that the movement of the armature will be responsive to the movement of the stylus bar. It to benoted in this connection that the pivotal mounting of the associated armature and stylus bar is well outside of the pole faces of the magnet, with the result that the pivotal mounting will not interfere to decrease the lines of force out by the vibrating armaturc.

A groove 31, milled in the top face of the upper arm of each magnet, extends at an angle thereto and communicates with the upper pole face for receiving edgewise a resilient disc 32 of rubber composition or the like. A slider plate 33, whi ch extends into the above mentioned groove, is adjustably secured to a boss 34, integral with the base member and extending at right angles thereto, by a cap screw which extends through a longitudinal aperture 36 of the slider plate. The end of the slider plate which is inserted into the groove is beveled to. form a point. By loosening the cap screw the slider plate may be moved longitudinally into the, groove, the pointed end thereof engaging the resilient disc 32 and pressing it against one side of the armature. The screw may then be tightened to hold the slider plate securely in this position. It is evident that, with a disc 32 pressing against each side of the armature, the vibration of the armature will be limited. It is also possible to use the means just described for centering the armature relative to the confronting pole faces.

This invention provides an improved electrical pick-up device in which the permanent magnets act as keepers for each other, thereby preventing them from naturally dying out. The efliciency of the device will, therefore, be maintained over a long period of time. The pivot pin mounting of the stylus bar and associated armature is well outside the magnetic path. Consequently, no part of the structure of the device will tend to decrease the available lines of force emerging from the pole faces of the magnet. A novel means is also provided for centering the armature between the confronting pole faces of the magnet and also limiting its amplitude of vibration.

I am aware that many changes may be made, and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore, do notpurpose limiting the patent granted hereon, otherwise than necessitated by the. prior art.

I claim as my invention:

1. In an electrical pick-up device, a support, complementary permanent magnets connected to the support and defining arms having confronting pole faces, each'of said magnets having poles of opposite polarity, a coil bet-ween the arms of the magnets, 21 vibratable armature extending through said coil and dis posed between the pole faces of the magnets, and a stylus bar operatively associated with the armature.

2. In an electrical pick-up device, a support, complementary permanent magnets connected to the support and defining arms having confronting pole faces, each of said magnets having poles of opposite polarity, a vibratable armature disposed between the confronting pole faces and terminating in stylus bar, a coil surrounding a portion of said armature, and means for varying the vibration of said armature relative to the pole faces.

8. In an electrical pick-up device, a support, a plug pin receptacle secured to said support, a pair of permanent magnets secured to the support, said magnets defining arms having confronting faces, an armature extending between said faces and terminating in a stylus bar, a coil disposed between the arms of said magnets and surrounding the armature, said coil having its terminals connected to said plug pin receptacle, and resilient means carried by certain of said arms for engaging said armature to hold it in spaced relation to said faces.

4. In an electrical pick-up device, a support, a pair of permanent horseshoe magnets on the support and arranged with the pole faces confronting and in spaced relation, each of said magnets having poles of opposite polarity, an armature pivotally connected to the support at a point outside the magnetic path and extending between the pole faces, said armature having a stylus associated therewith, and a coil surrounding said armature.

5. An electrical pick-up device including a pair of confronting horseshoe magnets, each of said magnets having poles of opposite polarity, and a vibratable armature between the confronting pole faces of said magnets.

6. An electrical pick-up device including a supporting structure, a pair of permanent horseshoe magnets on said structure and arranged with their pole faces confronting, two of the adjacent pole faces each having a groove extending therefrom, a vibratable armature extending between the pole faces and in spaced relation thereto, a resilient disc in each of said grooves, and means supported on said structure for moving said disc into engagement with said armature to limit its amplitude of vibration.

7. An electrical pick-up device including a support, a plug receptacle secured to said support and having a pair of insulated slotted sleeves therein for receiving the pins of a connection plug, a pair of permanent horseshoe magnets arranged with the pole faces confronting, a vibratable armature extending between said faces, a coil positioned between the arms of the magnets and surrounding said armature, and electrical conductors connecting the coil ends to said sleeves.

8. An electrical pickup device including a pair of confronting horseshoe magnets, an

armature, and means at one .end of said arma ture for mounting said armature for oscillatory movement between the confronting faces of said magnets, said means being outside the magnetic path between the confronting pole I v 7 races.

9. In an electrical pickup device, a pair of permanent horseshoe magnets arranged with their pole faces confronting, the north and south poles of one of said magnets being respectively positioned adjacent the south and north poles of the other magnet, and a vibratable armature spaced between the con fronting pole faces of said magnets.

10. In an electrical pickup device, a pair of permanent magnets arranged with their pole faces confronting, the polar relationship of said magnets being arranged in such a manner that each of said magnets will form a keeper for the other of said magnets, and an armature mounted for vibratory movement between said confronting pole faces.

11. In an electrical pickup device, a'su'pport, a pair of permanent horseshoe magnets secured to said support with the pole faces thereof in confronting relationship, an armature pivoted at one end on said support for oscillatory movement between said confronting pole faces, said pivot point being disposed outside the magnetic path of said magnets, a stylus bar associated with said armature, and a coil surrounding said armature.

12. In a device of the class described, a support, a pair of permanent horseshoe magnets secured to said support with the pole faces thereof in confronting relationship, an armature operatively associated with said magnets and terminating at one end in a stylus bar, said armature and stylus bar having a common pivotal mounting disposed outside the magnetic path of said magnets, and a coil surrounding said armature.

13. In an electrical pickup device, a supporting structure having means adapted for removably connecting the same to a tone arm, electromagnetic means carried by said supporting structure having conductors leading therefrom, a stud of insulating material secured to said supporting structure, and a plurality of spaced female members associated with said stud and adapted for engagement by male members carried by said tone arm, said male members being adapted for electrically connecting to corresponding conductors in said tone arm, each of said firstmentioned conductors being electrically connected to one of said female members.

14. In an electrical pickup device, a supporting structure, a pair of permanent horseshoe magnets supported on said structure with their pole faces confronting, two of said confronting pole faces each having a roove therein, a vibratable armature extending between the pole faces of said magnets, and means for limiting the vibration of said armature, said means con'iprising a resilient member in each of said grooves for engaging the armature, and members slidably supported on said structure for longitudinal movement, said members extending into the respective grooves for engaging the resilient members therein and forcing them against the armature.

15. An electrical pickup device including a supporting structure, a pair of permanent horseshoe magnets on said structure and ar ranged with confronting pole faces, two of said pole faces each having a groove extending at an angle therefrom, a rubber disc disposed edgewise in each of the grooves, a vibratable armature extending between the pole faces, and adjustable members s idably associated with the respective grooves for forcing the discs therein against the armature to limit the vibration thereof, each of said members being supported on said structure.

In testimony whereof I have hereunto sub- H scribed my name at Chicago, Cook County,

Illinois.

EDVARD TOM AN. 

